MRI has become one of the most important and prominent techniques in diagnostic clinical medicine. The most commonly used contrast agents (CAs) nowadays are thermodynamically and kinetically stable low molecular weight gadolinium complexes. However, current clinically available Gd-based contrast agents can be non-specific and inefficient. Indeed, current clinically available Gd-based contrast agents may suffer from drawbacks including rapid excretion and transient tissue retention.
Whilst macromolecular Gd complexes have been developed as intravascular CAs for blood pool and tumor angiogenesis because they may provide increased and prolonged contrast enhancement within the blood pool at low doses, large polymeric Gd complexes are associated with limitations, such as poorly defined architectures, unpredictable pharmacokinetics, and an increased possibility of Gd leakage from the Gd complex due to prolonged tissue retention.